<!DOCTYPE html>
<html lang="en">
<head>
    <style>
        #div01 {
            width: 100px;
            height: 50px;
            background-color: mediumvioletred;
            border: 1px solid rebeccapurple;
            display: none;
        }
    </style>
    <meta charset="UTF-8">
    <title>126邮箱</title>
</head>
<body>
    <label onmouseover=showTips() onmouseleave=hideTips()><input type="checkbox"> 自动登录</label>
    <div id="div01">
        请不要在网吧或公共地方选择该选项...
    </div>
</body>
<script>
    function showTips() {
        document.getElementById('div01').style.display = 'block';
    }
    function hideTips(){
        document.getElementById('div01').style.display = 'none';
    }
</script>
</html>